Composite intervertebral disc implants and methods for forming the same

ABSTRACT

Nucleus pulposus implants that are resistant to migration in and/or expulsion from an intervertebral disc space are provided. In one form of the invention, an implant includes a load bearing elastic body surrounded in the disc space by an anchoring, preferably resorbable, outer shell. In certain forms of the invention, the elastic body is surrounded by a supporting member, such as a band or jacket, and the supporting member is surrounded by the outer shell. Kits for forming such implants are also provided. In another form of the invention, an implant is provided that has locking features and optional shape memory characteristics. In yet another aspect of the invention, nucleus pulposus implants are provided that have shape memory characteristics and are configured to allow short-term manual, or other deformation without permanent deformation, cracks, tears, breakage or other damage. Methods of forming and implanting the implants are also described.

This application claims priority from U.S. patent application Ser. No.10/253,453, filed Sep. 24, 2002, which is a divisional applicationclaiming priority from U.S. patent application Ser. No. 09/650,525,filed Aug. 30, 2000 and issued Sep. 16, 2003 as U.S. Pat. No. 6,620,196;and from U.S. patent application Ser. No. 09/943,441, filed Aug. 30,2001, which is a continuation-in-part of U.S. patent application Ser.No. 09/650,525, referenced above, with all of said priority applicationsbeing incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to nucleus pulposus implants and methodsfor their implantation.

The intervertebral disc functions to stabilize the spine and todistribute forces between vertebral bodies. A normal disc includes agelatinous nucleus pulposus, an annulus fibrosis and two vertebral endplates. The nucleus pulposus is surrounded and confined by the annulusfibrosis.

Intervertebral discs may be displaced or damaged due to trauma ordisease. Disruption of the annulus fibrosis may allow the nucleuspulposus to protrude into the vertebral canal, a condition commonlyreferred to as a herniated or ruptured disc. The extruded nucleuspulposus may press on a spinal nerve, which may result in nerve damage,pain, numbness, muscle weakness and paralysis. Intervertebral discs mayalso deteriorate due to the normal aging process. As a disc dehydratesand hardens, the disc space height will be reduced, leading toinstability of the spine, decreased mobility and pain.

One way to relieve the symptoms of these conditions is by surgicalremoval of a portion or all of the intervertebral disc. The removal ofthe damaged or unhealthy disc may allow the disc space to collapse,which would lead to instability of the spine, abnormal joint mechanics,nerve damage, as well as severe pain. Therefore, after removal of thedisc, adjacent vertebrae are typically fused to preserve the disc space.Several devices exist to fill an intervertebral space following removalof all or part of the intervertebral disc in order to prevent disc spacecollapse and to promote fusion of adjacent vertebrae surrounding thedisc space. Even though a certain degree of success with these deviceshas been achieved, full motion is typically never regained after suchvertebral fusions. Attempts to overcome these problems have led to thedevelopment of disc replacements. Many of these devices are complicated,bulky and made of a combination of metallic and elastomeric components.Thus, such devices require invasive surgical procedures and typicallynever fully return the full range of motion desired.

More recently, efforts have been directed to replacing the nucleuspulposus of the disc with a similar gelatinous material, such as ahydrogel. However, there exists a possibility of tearing or otherwisedamaging the hydrogel implant during implantation. Moreover, oncepositioned in the disc space, many hydrogel implants may migrate in thedisc space and/or may be expelled from the disc space through an annulardefect, or other annular opening. A need therefore exists for moredurable implants, as well as implants that are resistant to migrationand/or expulsion through an opening in the annulus fibrosis. The presentinvention addresses these needs.

SUMMARY OF THE INVENTION

Nucleus pulposus implants that are resistant to migration in and/orexpulsion from an intervertebral disc space are provided. Accordingly,in one aspect of the invention, nucleus pulposus implants are providedthat include a load bearing elastic body sized for introduction into anintervertebral disc space and surrounded by a resorbable shell thatprovides the initial fixation for the elastic body within the discspace. The implant may include various surface features on its outersurface, including surface configurations or chemical modifications,that enhance the bonding between the outer surface of the implants andthe resorbable shell. Kits for forming such implants are also provided.In other forms of the invention, the elastic body may be surrounded by asupporting member wherein the supporting member is surrounded by theresorbable shell.

In yet another aspect of the invention, nucleus pulposus implants areprovided that have shape memory and are configured to allow extensiveshort-term deformation without permanent deformation, cracks tears orother breakage. In one form of the invention, an implant includes a loadbearing elastic body sized for placement into an intervertebral discspace. The body includes a first end, a second end and a central portionwherein the first end and second end are positioned, in a folded,relaxed configuration, adjacent to the central portion to form at leastone inner fold. The inner fold preferably defines an aperture. Theelastic body is deformable into a second, straightened, non-relaxedconfiguration for insertion through an opening in an intervertebral discannulus fibrosis. The elastic body is deformable automatically back intoa folded configuration after being placed in the intervertebral discspace. Advantageously, where the implant having shape memory is formedof a hydrogel material, or other hydrophilic material that may bedehydrated, the implant may be fully or partially dehydrated prior toinsertion such that it may be inserted through a relatively smallopening in the annulus fibrosis. The opening may, for example, be apre-existing defect or may be made by making a small incision.

In still other aspects of the invention, nucleus pulposus implantshaving locking features and optionally having shape memory are provided.In one embodiment, an implant includes a load bearing elastic bodyhaving a first end and a second end that are configured for matingengagement with each other. The implant has a first, lockedconfiguration wherein the first and second ends are matingly engaged toeach other. The implant may be configured into a second, straightenedconfiguration by application of external force for insertion through anopening in an intervertebral disc annulus fibrosis. When the implantincludes shape memory characteristics, it may be automaticallyconfigured, or otherwise returned, back into its first, lockedconfiguration after insertion through the opening in the annulusfibrosis and after any external force is removed, or may be placed intoits locked configuration by application of external force.

In other aspects of the invention, methods of implanting the nucleuspulposus implants of the present invention are provided. In one mode ofcarrying out the invention, a method includes providing the appropriateimplant, preparing the intervertebral disc space to receive the implantand then placing the implant into the intervertebral disc space. Wherethe implant includes a load bearing elastic body and an outer resorbableshell, a preferred method includes preparing the intervertebral discspace to receive the implant, introducing the elastic body forming thecore of the implant into the disc space wherein the body is surroundedin the disc space by a resorbable outer shell. The material forming theresorbable shell may be placed in the disc space prior to, after, or atthe same time as insertion of the elastic body. Alternatively, theelastic body may be surrounded by the outer shell prior to introductionof the elastic body into the intervertebral disc space.

It is an object of the invention to provide nucleus pulposus implants,and kits for their formation, that are resistant to migration in and/orexplusion from an intervertebral disc space.

It is a further object of the invention to provide nucleus pulposusimplants having shape memory that are configured to allow extensiveshort term manual, or other deformation without permanent deformation,cracks, tears, breakage or other damage.

It is yet another object of the present invention to provide nucleuspulposus implants having locking features.

It is a further object of the present invention to provide methods offorming and implanting the nucleus pulposus implants described herein.

These and other objects and advantages of the present invention will beapparent from the description herein.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts a side view of a cross-section of a nucleus pulposusimplant, including an elastic body 15 surrounded by an anchoring outershell 30, implanted in the intervertebral disc space of a disc.

FIG. 2 depicts a top, cross-sectional view of the nucleus pulposusimplant of FIG. 1.

FIG. 3 depicts a side view of a cross-section of the nucleus pulposusimplant of FIG. 1 after outer shell 30 has been resorbed and replaced byfibrous scar tissue 33.

FIG. 4 shows a top, cross-sectional view of the nucleus pulposus implantof FIG. 3.

FIG. 5 shows a side view of a cross-section of a nucleus pulposusimplant, including an elastic body 15 surrounded by a supporting member34, in the form of a band, wherein the supporting member is surroundedby an anchoring outer shell 30, implanted in the intervertebral discspace of a disc.

FIG. 6 depicts a side view of a cross-section of a nucleus pulposusimplant, including an elastic body 15 surrounded by a supporting member37, in the form of a jacket, wherein the supporting member is surroundedby an anchoring outer shell 30, implanted in the intervertebral discspace of a disc.

FIGS. 7A-7D depict various patterns of a supporting member of thepresent invention.

FIG. 8 depicts a side view of a cross-section of a nucleus pulposusimplant including an elastic body 15 surrounded by a supporting member34, taking the form of a band, that is further reinforced, or otherwisesupported, by straps 420 and 430. The implant is surrounded by ananchoring outer shell 30 and is shown implanted in the intervertebraldisc space of a disc.

FIG. 9 shows a top, cross-sectional view of the nucleus pulposus implantof FIG. 8.

FIG. 10 depicts a side view of an alternative embodiment of a nucleuspulposus implant of the present invention that includes peripheralsupporting band 34″ and securing straps 520, 530, 540 and 550 and issurrounded by an anchoring outer shell 30 and implanted in theintervertebral disc space of a disc.

FIG. 11 depicts a top, cross-sectional view of the nucleus pulposusimplant of FIG. 10.

FIG. 12 depicts a top view of an alternative embodiment of a nucleuspulposus implant having shape memory.

FIG. 13 shows a side view of the implant shown in FIG. 12.

FIGS. 14A-14J depict portions of nucleus pulposus implants with surfacemodifications. FIGS. 14A-14H show side views of top portions of theimplants, and FIG. 141 and FIG. 14J show top views of the views shown in14C and 14D, respectively.

FIGS. 15A-15N show top views of alternative embodiments of nucleuspulposus implants having shape memory in folded, relaxed configurations.

FIGS. 16A-16N depict top views of the implants shown in FIGS. 15A-15N,respectively, in unfolded, non-relaxed configurations.

FIG. 17 depicts a top view of an alternative embodiment of a nucleuspulposus implant of the present invention having a self-locking feature.The implant is shown in its locked, relaxed configuration.

FIG. 18 depicts a side view of the implant of FIG. 17.

FIG. 19 depicts a side view of the implant of FIG. 18 in an unfolded,non-locked, non-relaxed configuration.

FIG. 20 depicts one step in a method of implanting nucleus pulposusimplant 40 into intervertebral disc space 20 between vertebrae 21 and 22using a conventional implantation tool 310.

FIG. 21 depicts a top, cross-sectional view of a nucleus pulposusimplant 10 in its folded, relaxed configuration positioned inintervertebral disc space 20.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to preferred embodiments andspecific language will be used to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations and furthermodifications of the invention, and such further applications of theprinciples of the invention as illustrated herein, being contemplated aswould normally occur to one skilled in the art to which the inventionrelates.

The present invention provides prosthetic intervertebral disc nucleuspulposus implants that may fully or partially replace the natural, ornative, nucleus pulposus in mammals, including humans and other animals.In one aspect of the invention, implants are provided that areconfigured to resist expulsion or other migration through a defect, orother opening, in the annulus fibrosis and to resist excessive migrationwithin an intervertebral disc space. In certain forms, these implantscombine the advantages of an injectable/in-situ curing implant with apre-formed implant. For example, a nucleus pulposus implant may includea load bearing elastic body surrounded by an outer, preferablyresorbable or otherwise temporary, shell. The outer shell advantageouslyanchors the elastic body within the intervertebral disc space. Thesurface of the elastic body may include various surface features,including various macro-surface patterns, and chemical or physicalmodifications as described herein to further enhance fixation of theimplant to the outer resorbable shell. The surface features, such as themacro-surface patterns and physical modifications, for example, are alsoexpected to enhance fixation of the elastic body to surrounding tissuesuch that, in certain forms of the invention, no outer shell may beneeded.

In other aspects of the invention, nucleus pulposus implants havingshape memory that are configured to allow extensive short-term manual orother deformation without permanent deformation, cracks, tears, breakageor other damage are provided. In preferred forms of the inventionwherein the implants are formed from a hydrogel or other hydrophilicmaterial, the implants can not only pass through a relatively smallincision in the annulus fibrosis, but can also substantially fill andconform to the intervertebral disc space. In one form of the invention,an implant includes a load bearing elastic body with shape memory havingfirst and second ends that are positioned adjacent to a central portionto form at least one inner fold. The inner fold desirably defines anaperture.

In other embodiments of the invention, the shape memory implants areconfigured to form a spiral or other annular shape in the disc space,and may also be configured to have ends that matingly engage each otherfor further securing the implant in the disc cavity. Methods of makingand implanting the implants described herein are also provided.

As disclosed above, in a first aspect of the invention, a nucleuspulposus implant is provided that includes a load bearing elastic bodysized for introduction into an intervertebral disc space and surroundedby an outer, preferably resorbable, shell. Referring now to FIGS. 1 and2, prosthetic implant 10 includes a core load bearing elastic body 15disposed in intervertebral disc space 20, between vertebral body 21 and22 and surrounded by an outer shell 30. More specifically, elastic body15 has an outer surface 16 in contact with, and preferably bonded to, anouter shell 30 that may advantageously be resorbable, or otherwisetemporary. Outer surface 31 of outer shell 30 preferably conforms to theshape of the intervertebral disc space 20, being in contact with annulusfibrosis 5, and may completely surround elastic body 15 as seen in FIGS.1 and 2, although outer shell 30 may only partially surround elasticbody 15. As an example, upper, lower and/or lateral voids surroundingelastic body 15 may be filled in by outer shell 30, as long as theelastic body is in some way anchored, or otherwise fixed in place, bythe outer shell so as to prevent its expulsion from, or excessivemigration in, the disc cavity. Thus, outer shell 30 may be configured tofill the aforementioned voids. Additionally, inner surface 32 of outershell 30 preferably conforms to the shape of elastic body 15, andpreferably bonds to outer surface 16 of elastic body 15 as discussedbelow. In preferred embodiments, the elastic core and the outer shellsubstantially fill the disc cavity as further discussed below.

Outer shell 30 not only provides for a properly fit implant 10 withinintervertebral disc space 20 for maximum load-bearing, stress transfer,and bonding of the implant surface to the surrounding disc tissues forfixation against excessive migration, it also seals an annular defect 18for further resistance to migration and/or expulsion of the implant.Such sealing of the annular defect may also provide additional physicaland mechanical support to the disc. Furthermore, the injectable outershell material may provide intra-operative flexibility in fitting thecore elastic body of implant 10 within the disc space as it maycompensate for the differences in geometry and size between the discspace and the pre-formed core.

Outer shell 30 is preferably resorbable and, in such form, is preferablyreplaced with tissue, such as fibrous tissue and including fibrous scartissue, that may aid in permanently confining the load bearing elasticbody within the disc space. Referring now to FIGS. 3 and 4, tissue 33has replaced outer shell 30, and thus surrounds elastic body 15.Although elastic body 15 may be confined within the disc space with theaid of tissue 33, body 15 is expected to have some mobility for normalbiomechanics.

The dimensions of load bearing elastic body 15 may vary depending on theparticular case, but elastic body 15 is typically sized for introductioninto an intervertebral disc space. Moreover, elastic body 15 ispreferably wide enough to support adjacent vertebrae and is of a heightsufficient to separate the adjacent vertebrae. In order to providelong-term mechanical support to the intervertebral disc, the volume ofelastic body 15 in the disc space should be at least about 50%,preferably at least about 70%, further preferably at least about 80% andmore preferably at least about 90% of the volume of the entire discspace, the remaining volume occupied by outer shell 30. However, thevolume of elastic body 15 may be as large as about 99% of the volume ofthe intervertebral disc space, and thus about 99% of the volume ofimplant 10. Accordingly, the volume of outer shell 30 may be at leastabout 1% of the volume of the implant, but may range from about 1% toabout 50%. The appropriate size of implant 10 desired in a particularcase may be determined by distracting the disc space to a desired levelafter the desired portion of the natural nucleus pulposus and any freedisc fragments are removed, and measuring the volume of the distractedspace with an injectable saline balloon. The disc volume can also bemeasured directly by first filling the disc space with a known amount ofthe outer shell precursor material.

Elastic body 15 may be fabricated in a wide variety of shapes asdesired, as long as the body can withstand spinal loads and other spinalstresses. The non-degradable and preformed elastic body 15 may beshaped, for example, as a cylinder, or a rectangular block. The body mayfurther be annular-shaped. For example, implant 10′ in FIGS. 12 and 13has a spiral, or otherwise coiled, shape. The implant includes a firstend 23 and a second end 24. Elastic body 15 may also be shaped togenerally conform to the shape of the natural nucleus pulposus, or maybe shaped as further described below. Although elastic body 15 is shownas one piece in, for example, FIGS. 1-4, it may be made from one orseveral pieces.

Elastic body 15 may be formed for a wide variety of biocompatiblepolymeric materials, including elastic materials, such as elastomericmaterials, hydrogels or other hydrophilic polymers, or compositesthereof. Suitable elastomers include silicone, polyurethane, copolymersof silicone and polyurethane, polyolefins, such as polyisobutylene andpolyisoprene, neoprene, nitrile vulcanized rubber and combinationsthereof. The vulcanized rubber described herein may be produced, forexample, by a vulcanization process utilizing a copolymer produced asdescribed, for example, in U.S. Pat. No. 5,245,098 to Summers et al.from 1-hexene and 5-methyl-1,4-hexadiene. Suitable hydrogels includenatural hydrogels, and those formed from polyvinyl alcohol, acrylamidessuch as polyacrylic acid and poly(acrylonitrile-acrylic acid),polyurethanes, polyethylene glycol, poly(N-vinyl-2-pyrrolidone),acrylates such as poly(2-hydroxy ethyl methacrylate) and copolymers ofacrylates with N-vinyl pyrrolidone, N-vinyl lactams, acrylamide,polyurethanes and polyacrylonitrile, or may be other similar materialsthat form a hydrogel. The hydrogel materials may further be cross-linkedto provide further strength to the implant. Examples of polyurethanesinclude thermoplastic polyurethanes, aliphatic polyurethanes, segmentedpolyurethanes, hydrophilic polyurethanes, polyether-urethane,polycarbonate-urethane and silicone polyether-urethane. Other suitablehydrophilic polymers include naturally-occurring materials such asglucomannan gel, hyaluronic acid, polysaccharides, such as cross-linkedcarboxyl-containing polysaccharides, and combinations thereof. Thenature of the materials employed to form the elastic body should beselected so the formed implants have sufficient load bearing capacity.In preferred embodiments, a compressive strength of at least about 0.1Mpa is desired, although compressive strengths in the range of about 1Mpa to about 20 Mpa are more preferred.

Outer shell 30 may be formed from a wide variety of biocompatible,preferably elastic, elastomeric or deformable natural or syntheticmaterials, especially materials that are compatible with elastic body15. The outer shell materials preferably remain in an uncured,deformable, or otherwise configurable state during positioning of theelastic body in the interverterbral disc space, and should preferablyrapidly cure, become harder or preferably solidify after beingintroduced into the intervertebral disc space, or, in other embodiments,prior to positioning of the elastic body in the intervertebral discspace. In preferred embodiments, the outer shell materials may remaindeformable after they harden or otherwise solidify. Suitable materialsthat may be used to form the outer shell include tissue sealants oradhesives made from natural or synthetic materials, including, forexample, fibrin, albumin, collagen, elastin, silk and other proteins,polyethylene oxide, cyanoacrylate, polylactic acid, polyglycolic acid,polypropylene fumarate, tyrosine-based polycarbonate and combinationsthereof. Other suitable materials include demineralized bone matrix.These precursor materials may be supplied in liquid, solution or solidform, including gel form.

Elastic body 15 may include a variety of surface features on outersurface 16, including chemical modifications and surface configurations,to provide surface features that advantageously improve the bondingbetween outer surface 16 of the elastic body and inner surface 32 ofouter shell 30. In one form of the invention, outer surface 16 ischemically modified utilizing, for example, chemical groups that arecompatible with the materials used to form outer shell 30. Suitablechemical modifications include, for example, surface grafting ofreactive functional groups, including hydroxyl, amino, carboxyl andorganofunctional silane groups. The groups may be grafted by methodsknown to the skilled artisan. Other modifications include pre-coatingwith a primer, preferably one that is compatible with the outer shellmaterial, such as a layer of adhesive, sealing or other materials usedfor forming the outer shell described above.

In yet another form of the invention, elastic body 15 may include a widevariety of surface configurations, such as macro-surface patterns, orprotuberances, as seen in FIGS. 14A-14J, showing side views or top viewsof top portions of elastic bodies with various surface features.Referring now to FIGS. 14A-14J, the pattern may be a dove-tail pattern200, a circular pattern 205, a square pattern 210, a conical pattern215, various wave patterns 220 and 225 and random, irregular patterns230. In other embodiments, a fiber 240 may be disposed in elastic body241 and may project from the surface 242 thereof to form a fibrouspattern 235. Fiber 240 may be disposed as a loop projecting from thesurface of the elastic body, its ends may project from the surface ofthe elastic body, or the fiber may have a wide variety of otherappropriate configurations. The fiber may be a short, polymeric fiber,such as one that is cut to less than about one inch. The fiber may,alternatively, be a continuous polymeric fiber. The fiber may further bebraided, and may be woven or non-woven. The macro-surface patterns arepreferably formed during formation of elastic body 15. However, outersurface 16 of elastic body 15 may also be physically modified afterformation of elastic body 15 by, for example, laser drilling or thermaldeformation. Physical modifications include, for example, amicrotexturized surface formed by bead-blasting, plasma etching orchemical etching. Procedures for modifying various surfaces in thismanner are well known in the art.

In certain forms of the invention, the implant may include only elasticbody 15 having one or more of the outer surface features as describedabove, without the outer resorbable shell. The surface features areexpected to provide a certain level of fixation to the surroundingtissues for improved resistance to migration and/or expulsion.

In yet other forms of the invention, the implant may include an elasticbody that is surrounded by a supporting, or otherwise constraining,member wherein the supporting member is surrounded by a resorbable shellas described herein. Referring now to FIG. 5, implant 400 includes aload bearing elastic body 15 that is surrounded by a supporting member34. In one form, supporting member 34 may be a preferably flexible,peripheral supporting band that is disposed circumferentially aboutelastic body 15 as seen in FIG. 5, leaving upper and lower surfaces 35and 36, respectively, of elastic body 15 free from the supporting band.

As seen in FIG. 5, portions of upper and lower surfaces 35 and 36,respectively, of elastic body 15 are exposed to directly contact outershell 30. This exposure minimizes the amount of material needed toconstruct the supporting member, yet still effectively provides, forexample, lateral support. Although the amount of the upper and lowersurfaces of elastic body 15 that are exposed may vary, typically atleast about 50%, preferably at least about 70%, more preferably at leastabout 80% and most preferably at least about 90% of the surfaces areexposed.

In yet another embodiment shown in FIG. 6, nucleus pulposus implant 500,that includes elastic body 15 as described above, is reinforced withsupporting member 37, which takes the form of a jacket. The jacketpreferably completely surrounds elastic body 15.

Suitable supporting members, including reinforcing outer bands, covers,or other jackets, may be formed from a wide variety of biocompatiblepolymers, metallic materials, or combination of materials that form astrong but flexible support to prevent excessive deformation, includinglateral (horizontal) deformation, of the core under increasingcompressive loading. Suitable materials include non-woven, woven,braided, or fabric materials made from polymeric fibers includingcellulose, polyethylene, polyester, polyvinyl alcohol,polyacrylonitrile, polyamide, polytetrafluorethylene, polyparaphenyleneterephthalamide, and combinations thereof. Other suitable materialsinclude non-reinforced or fiber-reinforced elastomers such as silicone,polyurethane, copolymers of silicone and polyurethane, polyolefins,including polyisobutylene and polyisoprene, neoprene, nitrile,vulcanized rubber, and combinations thereof. In a preferred form of theinvention, a combination, or blend, of silicone and polyurethane isused. Furthermore, the vulcanized rubber is preferably produced asdescribed above for the nucleus pulposus implants. Supporting members 34and 37 are advantageously made from a porous material, which, in thecase of an elastic body made from a hydrogel, or other hydrophilicmaterial, allows fluid circulation through the elastic core body toenhance pumping actions of the intervertebral disc. Supporting membersmay further be formed from carbon fiber yarns, ceramic fibers, metallicfibers or other similar fibers as described, for example, in U.S. Pat.No. 5,674,295.

FIGS. 7A-7D show supporting bands of various patterns, typically madefrom various braided materials (bands 25, 26 and 27), or porousmaterials (band 28), as described above. It is also understood thejackets may also be formed of such patterns. It is realized that thebraided materials may also be porous.

Supporting members 34 and 37 preferably decrease lateral deformation,compared to deformation of an implant without the supporting member, asdesired. Supporting members 34 and/or 37 may, for example, decreaselateral deformation by at least about 20%, preferably at least about40%, more preferably by at least about 60% and most preferably by atleast about 80%. An implant, such as one that includes an elastic body,having such a supporting member will be flexible and otherwise resilientto allow the natural movements of the disc and provides shock absorptioncapability at low to moderate applied stress, but will resist excessivedeformation for disc height maintenance under high loading conditions.As described herein in the case of a lumbar disc, for example, lowapplied stress includes a force of about 100 Newtons to about 250Newtons moderate stress includes a force of about 250 Newtons to about700 Newtons, and high loading conditions, or high stress, includes aforce of above about 700 Newtons. In preferred forms of the invention,the supporting member is flexible, in that it may be folded, orotherwise deformed, but is substantially inelastic, so that the implantis more fully reinforced or otherwise supported.

The elastic body may be covered by the jacket supporting member, or theband supporting member may be wrapped around the circumference of theelastic body. In a form of the invention wherein the elastic body isformed from a hydrogel, or similar hydrophilic material, the hydrogelmay be dehydrated a desired amount prior to being covered by the jacket,or prior to wrapping the band around the circumference of the hydrogelbody. The hydrogel elastic body may be exposed to saline outside of thebody, or may be inserted into the disc space wherein it will be exposedto body fluids in situ, and the body will absorb water and swell. Inreference to the peripheral band supporting member, the swelling orexpansion of the hydrogel elastic body in the horizontal direction iscontrolled by the amount of slack designed in the band. After thelimited allowable horizontal expansion is reached, the elastic body isforced to expand mostly in the vertical direction until reachingequilibrium swelling under the in vivo load. As the upper and lowersurfaces of the elastic body are not substantially constrained, thevertical expansion is mainly controlled by the applied stress and thebehavior of the hydrogel material.

In yet other forms of the invention, an implant reinforced with aperipheral supporting band as described above that is surrounded by aresorbable outer shell may be further reinforced with one or morestraps. The straps may be advantageous in preventing the peripheralsupporting band described herein from slipping, or otherwise sliding offthe implant. Referring now to FIGS. 8 and 9, at least one strap 420extends along upper surface 35 and at least one strap 430 extends alonglower surface 36 of elastic body 15 of implant 400. Ends 421 of strap420 and ends 431 of strap 430 are each preferably connected, orotherwise attached, to peripheral supporting band 34′. The point ofattachment may be any location that will secure the strap, including atthe upper margins 138 of the band, lower margins 139 of the band or anyregion between the upper and lower margins. Although two straps 420 and430 are shown extending along upper surface 35 and lower surface 36,respectively, in FIGS. 8 and 9, one continuous strap may be utilizedthat extends completely around the implant, or the strap utilized may bein one, two or multiple pieces, as long as the combination of straps aresufficient to prevent excessive slipping and or sliding of thesupporting band. Furthermore, more than one strap may extend along uppersurface 35 and more than one strap may extend along lower surface 36 ofelastic body 15, as seen, for example, in FIGS. 10 and 11 of implant500, wherein straps 520, 530, 540 and 550 are shown attached, orotherwise connect to supporting member 34″. It is realized that thestraps may be present in one or more pieces. For example, straps 520 and530 may form a single strap, as may straps 540 and 550, or may allcombine to form a single strap.

In other aspects of the invention, kits designed for forming theintervertebral disc nucleus pulposus implants that include the outershell described above are provided. In one form, a kit may include aload bearing elastic body as described above, along with a container ofmaterial to form the outer, preferably resorbable, shell. The materialmay be selected from the materials as described above. Moreover, thecontainer that houses the material that forms the shell may be made froma wide variety of materials that are compatible with the outer shellmaterial, including glass and plastic. The kit may further include asupporting member, such as a supporting band, jacket or other outercover as described above. Generally, the kits include sterile packagingwhich secures the kit components in spaced relation from one anothersufficient to prevent damage of the components during handling of thekit. For example, one may utilize molded plastic articles known in theart having multiple compartments, or other areas for holding the kitcomponents in spaced relation.

In a further aspect of the invention, nucleus pulposus implants areprovided having shape memory that are configured to allow extensiveshort-term manual, or other, deformation without permanent deformation,cracks, tears, breakage or other damage, that may occur, for example,during placement of the implant into an intervertebral disc space.Referring now to FIGS. 15A and 16A, in one form of the invention,implant 40 includes a load bearing elastic body 41 with shape memory andhaving a first end 42 and a second end 43 that are positioned adjacentto a central portion 44 to form at least one inner fold 45. Inner fold45 preferably defines at least one aperture 46 which is advantageouslyarcuate. The elastic body is deformable, or otherwise configurable,manually, for example, from this first folded, or otherwise relaxedconfiguration shown in FIG. 15A into a second, substantiallystraightened, or otherwise non-relaxed configuration shown in FIG. 16Afor placement into the intervertebral disc space. As elastic body 41 hasshape memory, it returns by itself, automatically, back into the firstfolded, relaxed configuration once manual or other force is no longerexerted on the body. These implants therefore provide improved handlingand manipulation characteristics in that they may be deformed,configured and otherwise handled by an individual without resulting inany breakage or other damage to the implant.

Further describing the shape memory nucleus prosthesis implant 40,implant 40 includes surface depressions 47, or other surfaceirregularities as more fully described below, that form inner fold 45when the implant is in its relaxed configuration. Ends 42 and 43 haveend surfaces 42 a and 43 a, respectively, that are generally flat, andsubstantially parallel, or perpendicular in other forms, to an axis Xpassing through the width of the implant in its relaxed configuration,wherein the ends may abut each other as seen in FIGS. 15A, 15B and15E-15N. The ends of the implant may each alternatively abut the centralportion of the implant, as shown for implants 60 and 70 in FIGS. 15C and15D, respectively, to form a generally bi-lobed or binocular-shapedimplant.

Alternatively, in other forms of the invention, one end of the implantmay be tapered, or otherwise specifically shaped, and the other end maybe shaped complementary to the tapered, or otherwise shaped, end.Moreover, either one or both sides 96 a and 96 b of the ends of thenucleus pulposus implant may be tapered. For example, and as seen inFIGS. 15F and 16F, both sides of end 93 of implant 90 are tapered toform a pointed end, such as a generally V-shaped end, thatadvantageously fits into a complementary-shaped (e.g., V-shaped)depression 95 defined by end 92. An implant having only one inner foldthat defines one aperture and ends that are similarly configured as ends92 and 93 is shown in FIGS. 15J and 16J. As another example, one side ofeach of the ends of the implant may be oppositely tapered as seen inFIGS. 15G and 16G. That is, side 108 a of end 102 of implant 100 andopposite side 109 b of end 103 are tapered as seen in FIGS. 15G and 16G.End surfaces 102 a and 102 b of implant 100 are transverse to axis Xwhen the implant is in its relaxed configuration shown in FIG. 15G. Inthose embodiments where the ends of the implants are tapered, orotherwise shaped, it is preferred that, when the ends of the implantscontact each other or the central or other portion of the implant, animplant is formed that is uniform along the length of the implantthrough the region of contact.

Although the implant may assume a wide variety of shapes, it istypically shaped, in its folded, relaxed configuration, to conform tothe shape of the natural nucleus pulposus.

In yet other forms of the invention, the folding implant may have asurface that includes surface projections that further aid in allowingshort-term deformation of the implant without permanent deformation orother damage as described above. Referring now to FIGS. 15D and 16D,implant 70 includes a load bearing elastic body 71 having a first end72, a second end 73 and a central portion 74. Inner fold 75 defines anaperture 76 and includes an inner fold surface 77 having wrinkles, orprojections 78 thereon. Projections 78 of inner fold surface 77 extendinto aperture 76. These wrinkles advantageously facilitate stretching ofthe implant without deformation, cracking, tearing, breakage, or otherdamage when the implant is straightened or elongated for insertion intothe intervertebral disc space. In the embodiment shown in FIGS. 15D and16D, the wrinkles, or surface projections, extend along the entirelength of elastic body 71, including central portion 74. Other implantshaving wrinkled inner fold surfaces are seen in FIGS. 15E and 16E andother wrinkle configurations upon folding the implant are seen in FIGS.15K-15N and 16K-16N.

In certain preferred forms of the invention, the apertures defined bythe inner folds of the implants described above have a radius of atleast about 1 mm. Moreover, in other preferred forms of the invention, areinforcing material may be included at the inner fold surface tofurther improve the structural integrity of the implant. The reinforcingmaterial may be a fabric that is either woven, or non-woven, and may beformed from braided fibers for further strength. The reinforcingmaterial may be positioned on the inner fold surface, may projecttherefrom or may be entirely embedded under the inner fold surface. Theimplant may be formed as a single piece, or may be formed of more thanone piece that is connected to the other pieces that form the assembledimplant by fabric that may be made from braided or other fibers.Although these implants are designed to be used without an anchoringouter shell, they, as well as all of the implants described herein, mayform the core elastic body of an implant that includes the outer shelldescribed herein.

The implants may obtain their shape memory characteristics in a varietyof ways. For example, the implants may be formed in a mold into adesired final shape, and, when deformed from this final shape byapplication of an external force, will return to the final shape uponrelease of the force.

In yet another embodiment of the invention, a nucleus pulposus implantis provided that has a locking feature, with optional shape memorycharacteristics, and thus may also resist being expelled from the disccavity to some extent. In one form of the invention as seen in FIGS.17-19, an implant 300 includes a load bearing elastic body 301 having afirst end 302 and a second end 303. The ends are typically configuredfor mating engagement with each other. Elastic body 301 has a first,locked configuration wherein first end 302 and second end 303 arematingly engaged to each other as seen more particularly in FIG. 17.When elastic body 301 has shape memory characteristics, elastic body 301is deformable, manually, for example, into a second, substantiallystraightened, non-relaxed configuration for insertion into anintervertebral disc space, as seen in FIG. 19, and may automatically beconfigured or otherwise returned back into the first, locked, relaxedconfiguration after insertion due to its shape memory characteristics.In those cases where the elastic body does not have shape memorycharacteristics and the elastic body is configurable into a lockedand/or straightened configuration, and in those cases where the elasticbody has shape memory characteristics, the elastic body may also beplaced into its locked configuration with the assistance of externalforce.

More particularly describing one form of the invention, end 302 definesan internal channel 304 as seen in FIG. 19 whereas end 303 is configuredto conform to the shape of internal channel 304. The channel may takethe form of a wide variety of shapes, as long as the ends of the elasticbody may be matingly engaged to form a locked configuration. As seen inFIG. 19, the channel is somewhat hour-glass shaped. Manual, or otherforce, may be applied to end 303 so that it may be temporarily deformed,or configured, sufficiently to pass through narrowed passage 305 withininternal channel 304. Once properly positioned, end 303 will be securedwithin channel 304, as end edges 303 a and 303 b are braced againstchannel edges 304 a and 304 b, respectively. Alternatively, one end ofan implant with a locking feature may be friction-fit within theinternal channel present in the other end of the implant. Thefriction-fit may arise as a result of the relative size differencesbetween the inner diameter of the channel formed by one end and theouter diameter of the other end of the implant. Additionally, and/oralternatively, the outer surface of one end, and/or the inner surface ofthe channel defined by the other end, may include surface roughenings asdescribed herein that aid in achieving the friction-fit. The implant mayalso be constructed from the biocompatible polymeric materials asdescribed above.

When the implants are formed from an elastic material, such as ahydrogel, or other similar hydrophilic material, or include theresorbable outer shell, they may advantageously deliver desiredpharmacological agents. The pharmacological agent may be a growth factorthat may advantageously repair the endplates and/or the annulusfibrosis. For example, the growth factor may include a bonemorphogenetic protein, transforming growth factor-β (TGF-β),insulin-like growth factor, platelet-derived growth factor, fibroblastgrowth factor or other similar growth factor or combination thereofhaving the ability to repair the endplates and/or the annulus fibrosisof an intervertebral disc.

The growth factors are typically included in the implants intherapeutically effective amounts. For example, the growth factors maybe included in the implants in amounts effective in repairing anintervertebral disc, including repairing the endplates and the annulusfibrosis. Such amounts will depend on the specific case, and may thus bedetermined by the skilled artisan, but such amounts may typicallyinclude less than about 1% by weight of the growth factor. The growthfactors may be purchased commercially or may be produced by methodsknown to the art. For example, the growth factors may be produced byrecombinant DNA technology, and may preferably be derived from humans.As an example, recombinant human bone morphogenetic proteins (rhBMPs),including rhBMP 2-14, and especially rhBMP-2, rhBMP-7, rhBMP-12,rhBMP-13, and heterodimers thereof may be used. However, any bonemorphogenetic protein is contemplated including bone morphogeneticproteins designated as BMP-1 through BMP-18.

BMPs are available from Genetics Institute, Inc., Cambridge, Mass. andmay also be prepared by one skilled in the art as described in U.S. Pat.No. 5,187,076 to Wozney et al.; U.S. Pat. No. 5,366,875 to Wozney etal.; U.S. Pat. No. 4,877,864 to Wang et al.; U.S. Pat. No. 5,108,922 toWang et al.; U.S. Pat. No. 5,116,738 to Wang et al.; U.S. Pat. No.5,013,649 to Wang et al.; U.S. Pat. No. 5,106,748 to Wozney et al.; andPCT Patent Nos. WO93/00432 to Wozney et al.; WO94/26893 to Celeste etal.; and WO94/26892 to Celeste et al. All bone morphogenic proteins arecontemplated whether obtained as above or isolated from bone. Methodsfor isolating bone morphogenetic protein from bone are described, forexample, in U.S. Pat. No. 4,294,753 to Urist and Urist et al., 81 PNAS371,1984.

In other forms of the invention, the pharmacological agent may be oneused for treating various spinal conditions, including degenerative discdisease, spinal arthritis, spinal infection, spinal tumor andosteoporosis. Such agents include antibiotics, analgesics,anti-inflammatory drugs, including steroids, and combinations thereof.Other such agents are well known to the skilled artisan. These agentsare also used in therapeutically effective amounts. Such amounts may bedetermined by the skilled artisan depending on the specific case.

The pharmacological agents are preferably dispersed within the hydrogel,or other hydrophilic, implant for in vivo release, and/or, with respectto the implants with the resorbable outer shell, may be dispersed in theouter shell. The hydrogel can be cross-linked chemically, physically, orby a combination thereof, in order to achieve the appropriate level ofporosity to release the pharmacological agents at a desired rate. Theagents may be released upon cyclic loading, and, in the case of implantsincluding a resorbable outer shell, upon resorption of the shell. Thepharmacological agents may be dispersed in the implants by adding theagents to the solution used to form the implant, by soaking the formedimplant in an appropriate solution containing the agent, or by otherappropriate methods known to the skilled artisan. In other forms of theinvention, the pharmacological agents may be chemically or otherwiseassociated with the implant. For example, the agents may be chemicallyattached to the outer surface of the implant.

The implants described herein may have embedded therein small metalbeads or wire for x-ray identification.

Methods of forming and implanting the nucleus pulposus implantsdescribed herein are also provided. In one form of the invention, withrespect to implant 10 described above having the anchorable outer shell30, implant 10 may be formed by first forming elastic body 15 and thenforming the outer shell. Methods of forming elastic body 15 are wellknown in the art.

For example, if the elastic body is made of elastomeric materials, suchas powdered elastomers including, for example, styrene-ethylene/butyleneblock copolymers, the powdered elastomer may be placed into anappropriate mold and may be compressed and heated to melt the powder.The mold is then cooled to room temperature. If the elastic body is madefrom a hydrogel, such as a polyvinyl alcohol, the polyvinyl alcoholpowder may be mixed with a solvent, such as, for example, water ordimethylsulfoxide, or combinations thereof, and heated and shaken untila uniform solution is formed. The solution may then be poured into amold, such as a rubber mold, and may be cooled at an appropriatetemperature, such as about 0° C. to about −80° C., for several hours toallow for crystallization. After cooling, the hydrogel can be partiallyor completely hydrated by soaking and rinsing with water but, in certainpreferred embodiments, may remain dehydrated so that it may be insertedthrough a smaller aperture in the annulus fibrosis.

Prior to positioning the implant in the interverterbral disc space, anincision may be made in the annulus fibrosis, or one may take advantageof a defect in the annulus, in order to remove the natural nucleuspulposus and any free disc fragments within the intervertebral discspace. The disc space is then distracted to a desired level. Onceformed, and after preparing the disc space for receiving the implant,elastic body 15 may be implanted into the intervertebral disc spaceutilizing devices well known in the art and as described in U.S. Pat.Nos. 5,800,549 and 5,716,416. If the outer shell precursor material wasalready placed in the intervertebral disc space, excess precursormaterial may flow out of the disc space. This excess material should bepromptly removed before it sets or otherwise cures. The outer shellmaterial may be injected, or otherwise introduced, into the disc spaceutilizing devices that are well known in the art, such as syringes,sealant/caulk guns, automatic liquid injectors, and applicators thatinclude, for example, two separate syringes which allow for simultaneousmixing of the components in a static mixer and delivery to the site, andmay be injected either prior to or after introduction of the implantinto the disc space. Whether the outer shell material is introducedprior to or after introduction of the implant into the disc space, thedistractor is then removed, any excess precursor material seeping out ofthe disc space is removed and the precursor material within the discspace is cured to form the outer shell. It is noted that the elasticbody may already be surrounded by the outer shell, which may be in apartially or fully hardened state but preferably remains deformable,prior to introducing the elastic body into the intervertebral discspace.

In yet another form of the invention, a method for implanting aprosthetic intervertebral disc having shape memory is provided. In oneembodiment, an implant including a load bearing elastic body having afirst end and a second end positioned adjacent to a central portion toform at least one inner fold as described above is provided. The implant40, for example, may be deformed by, for example, manual force into asubstantially straightened, non-relaxed configuration for insertionthrough an aperture formed in the annular fibrosis as indicated in FIG.20, and as best seen in FIG. 21. The aperture may be formed throughdeterioration or other injury to the annulus fibrosis, or may be made bypurposely incising the annulus. The implant may then be positioned in adelivery tool 310 known in the art, such as that described in U.S. Pat.No. 5,716,416, and inserted through aperture 18 in annulus 19. As theimplant enters the intervertebral space 20 and is no longer subject tomanual force, it deforms back into its relaxed, folded configuration asseen in FIG. 21. A portion, or substantially all, of the natural nucleuspulposus may be removed from the intervertebral disc space, depending onthe circumstances, prior to introduction of the implant into theintervertebral disc space. When implanting an implant that includes alocking feature, or other implant with shape memory as described herein,a similar protocol is followed. Additionally, with respect to an implantwith a locking feature, the implant may be placed into the lockedconfiguration with external force, imposed by, for example, medicalpersonnel.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges and modifications that come within the spirit of the inventionare desired to be protected. In addition, all references cited hereinare indicative of the level of skill in the art and are herebyincorporated by reference in their entirety.

1. A method of improving the fit of an intervertebral disc nucleuspulposus implant, said method comprising: (a) implanting a load bearingelastic body in an intervertebral disc space; and (b) providing aroundsaid elastic body an amount of biocompatible material sufficient tosubstantially or completely fill the remaining intervertebral disc spacearound said body.
 2. The method of claim 1 wherein said outer shell isprovided by injecting a biocompatible material around said elastic body.3. The method of claim 2 wherein said injected biocompatible materialcures into a solid outer shell.
 4. The method of claim 3 wherein saidsolid outer shell is elastic.
 5. The method of claim 2 wherein saidinjected biocompatible material is an adhesive material.
 6. The methodof claim 5 wherein said biocompatible adhesive material is a resorbablematerial.
 7. The method of claim 5 wherein said biocompatible adhesivematerial is a non-resorbable material.
 8. The method of claim 5 whereinsaid biocompatible adhesive material is a natural material.
 9. Themethod of claim 5 wherein said biocompatible adhesive material is asynthetic material.
 10. The method of claim 5 wherein said biocompatibleadhesive material is a curable material.
 11. The method of claim 5wherein said biocompatible adhesive material is a non-curable material.12. The method of claim 2 wherein said injected biocompatible materialis a tissue sealant material.
 13. The method of claim 12 wherein saidbiocompatible tissue sealant material is a resorbable material.
 14. Themethod of claim 12 wherein said biocompatible tissue sealant material isa non-resorbable material.
 15. The method of claim 12 wherein saidbiocompatible tissue sealant material is a natural material.
 16. Themethod of claim 12 wherein said biocompatible tissue sealant material isa synthetic material.
 17. The method of claim 12 wherein saidbiocompatible tissue sealant material is a curable material.
 18. Themethod of claim 12 wherein said biocompatible tissue sealant material isa non-curable material.
 19. The method of claim 1 wherein said elasticbody fills at least about 50% of the intervertebral disc space.
 20. Themethod of claim 19 wherein said elastic body fills at least about 70% ofthe intervertebral disc space.
 21. The method of claim 20 wherein saidelastic body fills at least about 80% of the intervertebral disc space.22. The method of claim 21 wherein said elastic body fills at leastabout 90% of the intervertebral disc space.
 23. The method of claim 1wherein said outer shell has a volume of between 1% and 50% of thevolume of the composite implant.
 24. The method of claim 1 wherein saidload bearing elastic body comprises a member selected from the groupconsisting of elastomeric materials, hydrogels, and hydrophilicpolymers, or composites thereof.
 25. The method of claim 24 wherein saidload bearing elastic body comprises an elastomeric material selectedfrom the group consisting of silicone, polyurethane, copolymers ofsilicone and polyurethane, polyolefins, and vulcanized rubber.
 26. Themethod of claim 24 wherein said load bearing elastic body comprises ahydrogel comprising one or more materials selected from the groupconsisting of natural hydrogels, and hydrogels formed from polyvinylalcohol, acrylamides, polyurethanes, polyethylene glycol,poly(N-vinyl-2-pyrrolidone), acrylates, copolymers of acrylates withN-vinyl pyrrolidone, N-vinyl lactams, acrylamide, polyurethanes andpolyacrylonitrile.
 27. The method of claim 25 wherein said polyurethanecomprises one or more materials selected from the group consisting ofthermoplastic polyurethanes, aliphatic polyurethanes, segmentedpolyurethanes, hydrophilic polyurethanes, polyether-urethanes,polycarbonate-urethanes and silicone polyether-urethanes.
 28. The methodof claim 24 wherein said load bearing elastic body comprises ahydrophilic polymer comprising one or more materials selected from thegroup consisting of glucomannan gel, hyaluronic acid, andpolysaccharides.
 29. The method of claim 1 wherein said outer shellcomprises a material selected from the group consisting of fibrin,albumin, collagen, elastin, silk, polyethylene oxide, cyanoacrylate,polylactic acid, polyglycolic acid, polypropylene fumarate,tyrosine-based polycarbonate, and demineralized bone matrix.
 30. Themethod of claim 1 wherein said outer shell further includes apharmacological agent.
 31. The method of claim 30 wherein saidpharmacological agent comprises a growth factor or an agent effectivefor treating degenerative disc disease, spinal arthritis, spinalinfection, spinal tumor or osteoporosis.
 32. The method of claim 31wherein said growth factor comprises one or more members selected fromthe group consisting of bone morphogenetic protein, transforming growthfactor-β (TGF-β), insulin-like growth factor, platelet-derived growthfactor, and fibroblast growth factor.
 33. The method of claim 30 whereinsaid pharmacological agent comprises one or more members selected fromthe group consisting of antibiotics, analgesics, and anti-inflammatorydrugs, including steroids.
 34. The method of claim 1 wherein said outershell is introduced into said intervertebral disc space prior tointroducing said elastic body into said intervertebral disc space. 35.The method of claim 1 wherein said outer shell is introduced into saidintervertebral disc space after introducing said elastic body into saidintervertebral disc space.
 36. The method of claim 1 wherein said outershell is introduced into said intervertebral disc space at the same timeas said elastic body is introduced into said intervertebral disc space.37. The method of claim 36 wherein said elastic body is provided withsaid outer shell prior to introducing said elastic body into said discspace.
 38. The method of claim 1 wherein said load bearing elastic bodycomprises a load bearing elastic body sized for placement into anintervertebral disc space, said body having a first end, a second end, acentral portion, and a first configuration wherein said first end andsaid second end are positioned adjacent to said central portion to format least one inner fold, said elastic body configurable into a second,straightened configuration for insertion through an opening in anintervertebral disc annulus fibrosis, said body configurable back intosaid first configuration after said insertion; wherein said bodyprovides an implant having a substantially solid center when the body isin its first configuration.
 39. The method of claim 1 wherein said loadbearing elastic body comprises a load bearing elastic body having shapememory and sized for placement into an intervertebral disc space, saidbody having a first end, a second end, and a central portion; whereinsaid shape memory biases said body to a first configuration wherein saidfirst end and said second end are positioned adjacent to said centralportion to form at least one inner fold and to provide a substantiallysolid center core when the implant is in its first configuration; saidelastic body configurable into a second, straightened configuration forinsertion through an opening in an intervertebral disc annulus fibrosis;wherein said shape memory returns said body to said first configurationafter said insertion; wherein said elastic body has a surface thatincludes wrinkles, indents or projections that relieve stress andprevent cracking or tearing of the implant when the implant isstraightened for implantation.
 40. A repaired intervertebral discnucleus, comprising: (a) a load bearing elastic body surgicallyimplanted in an intervertebral disc space; and (b) an outer shell aroundsaid load bearing elastic body; wherein said outer shell comprises anamount of biocompatible material sufficient to substantially orcompletely fill the remaining intervertebral disc space.
 41. Therepaired intervertebral disc nucleus of claim 40 wherein said outershell comprises a biocompatible material that has been injected aroundsaid elastic body.
 42. The repaired intervertebral disc nucleus of claim41 wherein said injected biocompatible material has been cured into asolid outer shell.
 43. The repaired intervertebral disc nucleus of claim42 wherein said solid outer shell is elastic.
 44. The repairedintervertebral disc nucleus of claim 41 wherein said injectedbiocompatible material is an adhesive material.
 45. The repairedintervertebral disc nucleus of claim 44 wherein said biocompatibleadhesive material is a resorbable material.
 46. The repairedintervertebral disc nucleus of claim 44 wherein said biocompatibleadhesive material is a non-resorbable material.
 47. The repairedintervertebral disc nucleus of claim 44 wherein said biocompatibleadhesive material is a natural material.
 48. The repaired intervertebraldisc nucleus of claim 44 wherein said biocompatible adhesive material isa synthetic material.
 49. The repaired intervertebral disc nucleus ofclaim 44 wherein said biocompatible adhesive material is a curablematerial.
 50. The repaired intervertebral disc nucleus of claim 44wherein said biocompatible adhesive material is a non-curable material.51. The repaired intervertebral disc nucleus of claim 41 wherein saidinjected biocompatible material is a tissue sealant material.
 52. Therepaired intervertebral disc nucleus of claim 51 wherein saidbiocompatible tissue sealant material is a resorbable material.
 53. Therepaired intervertebral disc nucleus of claim 51 wherein saidbiocompatible tissue sealant material is a non-resorbable material. 54.The repaired intervertebral disc nucleus of claim 51 wherein saidbiocompatible tissue sealant material is a natural material.
 55. Therepaired intervertebral disc nucleus of claim 51 wherein saidbiocompatible tissue sealant material is a synthetic material.
 56. Therepaired intervertebral disc nucleus of claim 51 wherein saidbiocompatible tissue sealant material is a curable material.
 57. Therepaired intervertebral disc nucleus of claim 51 wherein saidbiocompatible tissue sealant material is a non-curable material.
 58. Therepaired intervertebral disc nucleus of claim 40 wherein said elasticbody is sized to fill at least about 50% of the intervertebral discspace into which the implant is desired to be implanted.
 59. Therepaired intervertebral disc nucleus of claim 58 wherein said elasticbody fills at least about 70% of the intervertebral disc space intowhich the implant is desired to be implanted.
 60. The repairedintervertebral disc nucleus of claim 59 wherein said elastic body fillsat least about 80% of the intervertebral disc space into which theimplant is desired to be implanted.
 61. The repaired intervertebral discnucleus of claim 60 wherein said elastic body fills at least about 90%of the intervertebral disc space into which the implant is desired to beimplanted.
 62. The repaired intervertebral disc nucleus of claim 40wherein said outer shell has a volume of between 1% and 50% of thevolume of the composite implant.
 63. The repaired intervertebral discnucleus of claim 40 wherein said load bearing elastic body comprises amember selected from the group consisting of elastomeric materials,hydrogels, and hydrophilic polymers, or composites thereof.
 64. Therepaired intervertebral disc nucleus of claim 63 wherein said loadbearing elastic body comprises an elastomeric material selected from thegroup consisting of silicone, polyurethane, copolymers of silicone andpolyurethane, polyolefins, and vulcanized rubber.
 65. The repairedintervertebral disc nucleus of claim 63 wherein said load bearingelastic body comprises a hydrogel comprising one or more materialsselected from the group consisting of natural hydrogels, and hydrogelsformed from polyvinyl alcohol, acrylamides, polyurethanes, polyethyleneglycol, poly(N-vinyl-2-pyrrolidone), acrylates, copolymers of acrylateswith N-vinyl pyrrolidone, N-vinyl lactams, acrylamide, polyurethanes andpolyacrylonitrile.
 66. The repaired intervertebral disc nucleus of claim64 wherein said polyurethane comprises one or more materials selectedfrom the group consisting of thermoplastic polyurethanes, aliphaticpolyurethanes, segmented polyurethanes, hydrophilic polyurethanes,polyether-urethanes, polycarbonate-urethanes and siliconepolyether-urethanes.
 67. The repaired intervertebral disc nucleus ofclaim 63 wherein said load bearing elastic body comprises a hydrophilicpolymer comprising one or more materials selected from the groupconsisting of glucomannan gel, hyaluronic acid, and polysaccharides. 68.The repaired intervertebral disc nucleus of claim 40 wherein said outershell comprises a material selected from the group consisting of fibrin,albumin, collagen, elastin, silk, polyethylene oxide, cyanoacrylate,polylactic acid, polyglycolic acid, polypropylene fumarate,tyrosine-based polycarbonate, and demineralized bone matrix.
 69. Therepaired intervertebral disc nucleus of claim 40 wherein said outershell further includes a pharmacological agent.
 70. The repairedintervertebral disc nucleus of claim 69 wherein said pharmacologicalagent comprises a growth factor or an agent effective for treatingdegenerative disc disease, spinal arthritis, spinal infection, spinaltumor or osteoporosis.
 71. The repaired intervertebral disc nucleus ofclaim 70 wherein said growth factor comprises one or more membersselected from the group consisting of bone morphogenetic protein,transforming growth factor-β (TGF-β), insulin-like growth factor,platelet-derived growth factor, and fibroblast growth factor.
 72. Therepaired intervertebral disc nucleus of claim 69 wherein saidpharmacological agent comprises one or more members selected from thegroup consisting of antibiotics, analgesics, and anti-inflammatorydrugs, including steroids.
 73. The repaired intervertebral disc nucleusof claim 40 wherein said load bearing elastic body comprises a loadbearing elastic body sized for placement into an intervertebral discspace, said body having a first end, a second end, a central portion,and a first configuration wherein said first end and said second end arepositioned adjacent to said central portion to form at least one innerfold, said elastic body configurable into a second, straightenedconfiguration for insertion through an opening in an intervertebral discannulus fibrosis, said body configurable back into said firstconfiguration after said insertion; wherein said body provides animplant having a substantially solid center when the body is in itsfirst configuration.
 74. The repaired intervertebral disc nucleus ofclaim 40 wherein said load bearing elastic body comprises a load bearingelastic body having shape memory and sized for placement into anintervertebral disc space, said body having a first end, a second end,and a central portion; wherein said shape memory biases said body to afirst configuration wherein said first end and said second end arepositioned adjacent to said central portion to form at least one innerfold and to provide a substantially solid center core when the implantis in its first configuration; said elastic body configurable into asecond, straightened configuration for insertion through an opening inan intervertebral disc annulus fibrosis; wherein said shape memoryreturns said body to said first configuration after said insertion;wherein said elastic body has a surface that includes wrinkles, indentsor projections that relieve stress and prevent cracking or tearing ofthe implant when the implant is straightened for implantation.
 75. A kitfor repairing an intervertebral disc nucleus, comprising a load bearingelastic body sized for introduction into an intervertebral disc space,and a container of biocompatible material sufficient to form an outershell that substantially or completely fills a disc nucleus space. 76.The kit of claim 75 wherein said material is curable.
 77. The kit ofclaim 75 wherein said material is resorbable.
 78. The kit of claim 75wherein said resorbable material comprises a material selected from thegroup consisting of fibrin, albumin, gelatin, collagen, elastin, silk,demineralized bone matrix, polyethylene oxide, polyethylene glycol,polyvinyl alcohol, polypropylene fumarate and combinations thereof. 79.The kit of claim 75 wherein said elastic body is comprised of a hydrogelmaterial.
 80. The kit of claim 75 wherein said elastic body is comprisedof a polymer selected from the group consisting of elastomers andhydrogels.